// Copyright (c) Appeon. All rights reserved.
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. 
// You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0.

using System;
using System.Data;
using System.Data.Common;
using JetBrains.Annotations;

namespace SnapObjects.Data.MySql
{
    public class MySqlStringTypeMapping : StringTypeMapping
    {
        private readonly int _maxSpecificSize;
        private const int UnicodeMax = 4000;
        private const int AnsiMax = 8000;

        /// <summary>
        ///     Initializes a new instance of the <see cref="MySqlStringTypeMapping" /> class.
        /// </summary>
        /// <param name="dbTypeName"> The name of the database type. </param>
        /// <param name="dbType"> The <see cref="DbType" /> to be used. </param>
        /// <param name="unicode"> A value indicating whether the type should handle Unicode data or not. </param>
        /// <param name="size"> The size of data the property is configured to store, or null if no size is configured. </param>
        public MySqlStringTypeMapping(
            [NotNull] string dbTypeName,
            [CanBeNull] DbType? dbType,
            bool unicode = false,
            int? size = null)
            : base(dbTypeName, dbType, unicode, size)
        {
            _maxSpecificSize = CalculateSize(unicode, size);
        }

        private static int CalculateSize(bool unicode, int? size)
        {
            return unicode
                           ? size.HasValue && size < UnicodeMax ? size.Value : UnicodeMax
                           : size.HasValue && size < AnsiMax ? size.Value : AnsiMax;
        }

        /// <summary>
        ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
        ///     directly from your code. This API may change or be removed in future releases.
        /// </summary>
        public override TypeMapping Clone(string dbTypeName, int? size)
        {
            return new MySqlStringTypeMapping(
                           dbTypeName,
                           this.DbType,
                           this.IsUnicode,
                           size);
        }

        /// <summary>
        ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
        ///     directly from your code. This API may change or be removed in future releases.
        /// </summary>
        protected override void ConfigureParameter(DbParameter parameter, IAdoDbParameter adoDbParameter)
        {
            // For strings and byte arrays, set the max length to the size facet if specified, or
            // 8000 bytes if no size facet specified, if the data will fit so as to avoid query cache
            // fragmentation by setting lots of different Size values otherwise always set to
            // -1 (unbounded) to avoid SQL client size inference.

            var value = parameter.Value;
            var length = (value as string)?.Length ?? (value as byte[])?.Length;

            parameter.Size = value == null || value == DBNull.Value || (length != null && length <= _maxSpecificSize)
                ? _maxSpecificSize
                : -1;
        }

        /// <summary>
        ///     Generates the SQL representation of a literal value.
        /// </summary>
        /// <param name="value">The literal value.</param>
        /// <returns>
        ///     The generated string.
        /// </returns>
        protected override string GenerateNonNullSqlLiteral(object value)
        {
            return this.IsUnicode
                           ? $"N'{this.EscapeSqlLiteral((string)value)}'" // Interpolation okay; strings
                           : $"'{this.EscapeSqlLiteral((string)value)}'";
        }
    }
}
